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11.fAY 21, 1982;
:J
ONE· YEAR PONDEROSA PINE SEEDLING
PRODUCES POLLEN
R. L.
DEVELICE AND
J. T. FISHER
ABSTRACT.-A grN'nhouse·grown Pinus ponderosa Var. sCOpulOTum produced pollen at the earlv
age of I year. Sires. is hypothesized as the cause of the precocious cone.production. Pollen ,iabii.
lIy le'ts were negativ...
Minimum age of staminate cone production in Pinus ponderosa var, seo­
pu[orum Engelm. (Rocky Mountain ponderosa pine) has not previously
been ascertained. Generally, onset of reproductive maturity does not occur
until an age of 6 to 20 years. However, Righter (1939) found that ovulate
cones may be produced as early as 5 years, but did not report a minimum
age for staminate cone development. Staminate cones were found by Righter
(1939) on P. ponderosa var. ponderosa Laws. (typical ponderosa pine) at 2
years. Because Rocky Mountain ponderosa pine currently is the object of
tree improvement research, reduction in breeding cycle length is of great
pranical importance. Production of precocious cone-bearing trees is a
means of shortening the generation time. Stress has been shown to induce
precocious cone-production (Pharis, 1977; Quirk, 1973; Sweet and Will,
1965) and as such was employed in this study.
MAn:R1Al.5 ANI> METHolls.-ln November 1977. Rocky Mountain ponderosa pine seed were
planted in Ray·Leach 65·,m' {·ontainer. and placed in a grN'nhouse at N,'w Mexico Slalt' l'ni"<,,.·
,it\" Las Cruces. New Mexico. The seed was a sample from a bulk .mpply collected from squlIrei
<ad,.., throughout the Sacramento Mountains. New Mexico. POlling media was ):1 mix (by
weight) of P('ill and v(,rmiculite. No pre· planting seed treatment was utililed. In order to induce
'II"". til{' greenhouse·grown seedlings were not fertilized, did not n'(eive supplemental light. were
watned at illfrequern intervals extending from 7 to 12 days, and the ,mall ('ornainers with "pen
bottoms cau,..d root confinement and root pruning.
RESULTS AND DISCUSSION.-!n July of 1978, three of the approximatel\' 600
seedlings had produced reproductive buds (total of five buds). During
November 1978, one reproductive bud burst on one seedling and produced a
polien bearing cone (Fig. I). The remaining buds aboned. No ovulate cones
were observed, but pine species typically initiate staminate cones earlier.
Slow rate of vegetative growth was indicated by mean heights of 7 em at I
year, less than one-third the growth commonly observed under optimal
conditions. Stress apparently was a factor in the seedlings slow growth and
seems the probable cause of the precocious cone-production. Previous stud­
ies involving seedlings of the same source grown under less stressful condi­
tions yielded no precocious cone production (unpubl.). The pollen pro­
duced was morphologically comparable to mature ponderosa pine. Pollen
from I-year seedlings averaged 37 mm across the bladders and 28 mm hom
cap to furrow, whereas pollen from mature trees measured 38 mm and 25
mm respectively.
212
FIG,
'h'lll)
The Southwestern Naturalist
L-Ont'·)'t'ar Rocky Mountain ponderosa pine with mature staminate cone (leI! sidt' of
and abont'fl reproductive bud (right side of stem).
The pollen was found non-viable by the distilled water (Dillon and Zobel,
1957) and tetrazolium chloride (Cook and Stanley, 1960) viability tests,
However. such tests must be interpreted with caution since they may fail to
adequately simulate germination conditions found in the micropyle of ovu­
late cones. Johri and Vasil (1961) found that germination may be enhanced
by natural secretions not duplicated in artificial media.
No crosses were made with the pollen because insufficient quantities were
produced, Although precocious seedlings frequently produce infertile repro­
ductive organs, viable pollen has been reported in P. mugo Turra (Mergen
and Cutting, 1957) and P. contorta Dougl. (Johnson and Critchfield, 1978).
The three seedlings with reproductive buds were transplanted to larger
containers. Any pollen produced in coming years will be used in crossing
experiments to determine w1'!ether it is functional and to study heritability
of early cone production.
New Mexico Agricultural Experiment Station Journal Article 798.
LITERATURE CITED
S, A.. AND R. G. STANLEY. 1960. Tetrazolium chloride as an indicator 01 pine pollen
germinabilit\'. Silvae Genet.. 9:134·136.
D,LLON. E, S.. AND B. J. ZOBEL
19!)1. A simple test lor viability of pine pollen. l Forestry.
!)!):31·32.
COOK,
DeVelice and Fisher-Pine Pollen Production
213
JOHNSON. L. C .. AND W. B. CRlTICHFlELD. 1978. The production of functional-pollen and
ovules by pine seedlings less that I year old. Forest Sci .• 2·1:467-468.
JOHRI. B. M.. AND I. K. VASIL. 1961. Physiology of polien. Bot. R..,·.. 27:235-381.
MERGEN. F.. AND S. G. CUTTING. 1957. Male flowers on one-year-old mugu pine seedlings.
Forest Sci., 3:355-356_
PHARIS. R. P. 1977. Promotion of flowering in the Pinaceae by hormones-a reality. Proc.
13th Lake States Tree Improv. Conf., USDA Forestry Serv. General Tech. Rep., NC-50:1­
10.
Qt:1RK. J. T. 1973. Cone production stimulus related to transplal1ling in red pine. Silvae
Genet., 22:71-72.
RIGHTER. F. I.
1939. Early flower production among the pines. J. Forestry. 39:935-938.
SWEET. G. B.. AND G. M. WILL.
1965. Precocious male cone produnion associaled with low
nutriel1l SlalUS in clones of Pinus radiata. Nature,206:i39.
Addu'sses of autholS: Dept. of Biology and Dept. 0/ HOTticulture. New Mexico State ('IIi"" Las
en" e.'. NM 880m.